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Biomedical subjects

D M Layton

Publications and source records attributed to D M Layton.

At least 37 records · Page 2Linked to original sources
PubMed1994

Haemophagocytic lymphohistiocytosis: experience at two U.K. centres.

Haemophagocytic lymphohistiocytosis (HLH) is a rare disorder of inappropriate macrophage activation. Both familial and sporadic forms, which may be infection-associated, are recognized. Between 1985 and 1991 we treated 23 cases of HLH (12 male, 11 female). There were eight familial cases, defined by a previously affected sibling and/or history of consanguinity, age 3 d to 15 months at presentation. The age of the remaining 15 cases varied from 1 month to 9.5 years. A potential viral trigger was identified in four cases (EBV, two; parvovirus B19, one; echovirus II, one) including one familial case. Six of eight (75%) patients who received supportive care alone, including all four familial cases, died within 6 months of presentation. Both long-term survivors in this group presented at an older age (7.5 and 8 years) and had proven or suspected virus-associated HLH. 15 patients were treated with etoposide (150-250 mg/m2 days 1-3 every 21 d) and methylprednisolone; 10 patients received intrathecal methotrexate in addition. In nine (60%) of these cases a complete (six) or partial (three) response was achieved, though one child suffered a fatal 'tumour lysis' syndrome. Overall mortality in the treated group was 66.6%, being highest (75%) in patients under 2 years at presentation compared to 33% in those over 2 years. Two of three familial and one of five sporadic cases relapsed and died 3 d to 20 months from diagnosis. Only one familial case survives at follow-up of 11 months. Of the five remaining survivors, two received allogeneic bone marrow transplantation (one matched related, one haploidentical) and are alive at 11 and 29 months. Three cases aged 2.5, 7.5 and 9.5 years remain in remission at 11, 20 and 25 months respectively. The high mortality of HLH supports a role for allogeneic BMT in selected cases, particularly those with a familial basis or under 2 years at presentation.

Bone Marrow↗
PubMed1993

Fetal plasma interferon gamma concentration in normal pregnancy.

OBJECTIVE: Our purpose was to investigate changes with gestation in fetal plasma interferon gamma concentration. STUDY DESIGN: A cross-sectional study at the Harris Birthright Research Centre for Fetal Medicine, London, was performed. Enzyme-linked immunoassay was used to measure plasma concentration in 54 fetal blood samples obtained by cordocentesis or cardiocentesis at 12 to 37 weeks' gestation. RESULTS: The concentration of interferon gamma in fetal plasma decreased exponentially from a mean of 1.2 U/ml at 12 weeks' gestation to a mean of 0.5 U/ml at 37 weeks (r = 0.460, p < 0.001). CONCLUSIONS: The presence of high levels of fetal interferon gamma in the first trimester suggests that it may play an important role in early fetal immunologic development. Furthermore, this study has established reference ranges for interferon gamma that may be of value in the prenatal diagnosis of congenital infection.

Cross-Sectional Studies↗
PubMed1992

Preimplantation diagnosis of a human beta-globin transgene in biopsied trophectoderm cells and blastomeres of the mouse embryo.

The preimplantation diagnosis of a HbSA-globin transgene in biopsied trophectoderm cells and blastomeres in embryos using a transgenic mouse model for the trait of human sickle-cell anaemia has been undertaken. A sensitive procedure was developed for the amplification of the human beta-globin gene sequence flanking the sickle mutation. Polymerase chain reaction (PCR) assays were undertaken on one to five biopsied trophectoderm cells and isolated blastomeres of the preimplantation mouse embryo. After biopsy the blastocysts were cultured whilst the cells were analysed for the presence of the transgene, and a high proportion (82-91%) were viable as assessed by the presence of a blastocoele cavity within a 5-h period. The majority of the biopsied cultured blastocysts were frozen and used to confirm the diagnosis; 90 biopsied cultured blastocysts were transferred to pseudopregnant recipients and 34% established pregnancy. Material from day 13.5 post-coitum fetuses was also used to confirm the original diagnosis. The time (4-5 h) required to carry out the analysis obviates a need for extended culture or cryopreservation of the biopsied embryo. In individual experiments under optimal conditions, the presence of the transgene in biopsied cells was detected with 100% accuracy, and the PCR analysis was sensitive at the 1-cell level. The overall success rate of diagnosis and confirmation of the presence or absence of the human beta-globin sequence in the biopsied embryo was 70%. Over the entire experimental period (14 months) DNA contamination from a variety of sources did occasionally occur; the methods used to overcome this problem are discussed.

Anemia, Sickle Cell↗
PubMed1992

Analysis of lymphocyte phenotypes in cord blood from early gestation fetuses.

Using cord blood samples obtained from fetuses between 16 and 40 weeks gestation, we have used a lysed whole blood flow cytometric technique to study the natural history of lymphocyte phenotypes known to be highly represented in cord blood at birth. The majority (51.0 +/- 14.7%) of lymphocytes expressed CD45RA, a marker of 'virgin' cells and there was a correlation between increasing percentages of CD45RA+lymphocytes and gestational age (r = 0.44, P < 0.01). Few cells (8.5 +/- 4.2%) expressed the CD45RO marker of primed lymphocytes and very few (1.0 +/- 0.7%) co-expressed CD45RA and RO, indicating little traffic between the two maturation markers. The percentage of B lymphocytes co-expressing CD5 was high in the fetal circulation (55.5 +/- 10.5%) compared with healthy adults (23.2 +/- 14.3%; P < 0.00001) and the level of CD5+ B cells declined with gestational age in an exponential manner (r = -0.45, P < 0.05). Similarly, levels of T lymphocytes expressing the gamma delta T cell receptor (TCR) declined exponentially (r = -0.59, P < 0.005). These results demonstrate that lymphocytes remain almost entirely unprimed before birth. In addition, CD5+ B lymphocytes and TCR-gamma delta+ T lymphocytes decline exponentially towards birth, in a manner suggesting that they may be seeding peripheral sites such as the spleen, skin and mucosae.

Antigens, CD↗
PubMed1992

Blood leucocyte count in the human fetus.

Total and differential leucocyte counts were measured in cord blood samples obtained by cordocentesis (n = 316) or at elective caesarean section (n = 11) from normal fetuses of between 18 and 40 weeks' gestation. The total fetal leucocyte count increased exponentially from 2.8 x 10(9)/l at 18 weeks to 11.8 x 10(9)/l at term. The lymphocyte and monocyte counts increased linearly and the number of neutrophils increased exponentially from a mean value of 0.2 x 10(9)/l at 18 weeks to 0.8 x 10(9)/l at 31 weeks and then 8.5 x 10(9)/l at term. Early myeloid cells, eosinophils, and basophils were observed in 24%, 55%, and 15% of the blood films respectively; they contributed less than 2% to the total leucocyte count and there were no significant changes with gestation. The physiological leucopenia observed in fetuses early in the third trimester may partly explain the predisposition of premature neonates to infection.

Blood Cell Count↗
PubMed1992

Fetal leucocyte count in rhesus disease.

The effect of fetal anaemia on the total and differential leucocyte counts was studied by examining blood samples obtained by cordocentesis from 177 previously untransfused rhesus affected fetuses at 17-36 weeks' gestation. The mean fetal total leucocyte, lymphocyte, and monocyte counts were significantly lower than the corresponding values in normal controls and there were significant associations between the decrease in these cells and the degree of fetal anaemia. Possible mechanisms for leucopenia include (i) stimulation of erythroid progenitor production at the expense of production of myeloid progenitors, (ii) non-specific haemophagocytosis, or (iii) general suppression of haemopoiesis. Further understanding of the underlying mechanism and the implications of leucopenia as well as the previously reported thrombocytopenia and anaemia may provide a basis for improved antenatal and/or postnatal treatment.

Blood Cell Count↗
PubMed1991

Cross-lineage rearrangement of antigen receptor genes in atypical chronic myeloid leukemia.

The configuration of immunoglobulin (Ig) and T-cell receptor (TCR) genes was investigated in a case of atypical chronic myeloid leukemia (aCML) lacking a cytogenetically detectable Philadelphia chromosome and molecular evidence of breakpoint cluster region (bcr) rearrangement as determined by 5' and 3' bcr gene probes. Dual clonal rearrangement of Ig-heavy (H) and TCR-delta chain genes was identified. The genes for TCR-gamma and beta chain as well as Ig-kappa (k) chain were in germline configuration. These findings indicate transformation to have occurred in a hemopoietic stem cell with the capacity for antigen receptor gene rearrangement. The demonstration of cross-lineage rearrangement of both Ig and TCR genes lends support to evidence from G6PD alloenzyme studies that the target of transformation in aCML is an early stem cell not yet irreversibly committed to myeloid differentiation. Further studies are indicated to ascertain whether antigen receptor gene rearrangement constitutes a molecular marker useful in the diagnosis of aCML.

Aged↗
PubMed1990

Clinicopathological features of acute undifferentiated leukaemia with a stem cell phenotype.

Over a 4 1/2-year period, 141 patients with acute leukaemia had morphologic, immunophenotypic and cytochemical studies performed at King's College Hospital. Seven cases were noted to have blast cells which did not express myeloid or lymphoid antigens or cytochemical staining indicative of differentiation but were HLA DR and CD 34 positive. Based on these criteria we have used the term stem cell acute leukaemia to denote these patients. There were five women and two men with a median age of 61 years (16-86). Presentation marrows were heavily infiltrated with blasts (greater than 95% in 6/7) which were usually pleomorphic. Type 2 blasts. Auer rods and dysplastic features were absent. Two of six cases studied showed clonal karyotypic abnormalities. Four patients were treated with high dose chemotherapy. Three of these achieved a complete remission but relapsed at 3, 6 and 7 months respectively. The median survival of the group was 7 months (2-12). We conclude that the stem cell acute leukaemias are a distinct clinicomorphological group which appear to have a poor prognosis with conventional chemotherapy.

Acute Disease↗
PubMed1990

Mutation of the human FMS gene (M-CSF receptor) in myelodysplastic syndromes and acute myeloid leukemia.

We studied 41 patients with myelodysplastic syndromes or acute myeloid leukemia to assess the presence of point mutations in the human FMS gene (M-CSF receptor). Using the polymerase chain reaction and hybridization of oligonucleotide probes to the amplified sequences, we have detected mutations in eight of 41 patients, at codons 301 and 969. In vitro work has highlighted mutations at these codons as being oncogenic. We now report the detection of potentially activating mutations of the human FMS gene in vivo. The consequence of these mutations in the multistep pathogenesis of myeloid malignancy and their relevance to prognosis remains to be determined.

Alleles↗
PubMed1989

Myelofibrosis in primary myelodysplastic syndromes: a clinico-morphological study of 10 cases.

We describe 10 cases of primary myelodysplastic syndrome in which marrow fibrosis was striking at presentation. All the cases showed trilineage dysplasia with increased megakaryopoiesis and marked reticulin fibrosis. Significant organomegaly was notably absent. This association has hitherto not been highlighted and it is important to distinguish these cases from those of idiopathic myelofibrosis with which they may be confused. Furthermore, their comparatively long survival distinguishes these cases from those previously described as acute myelodysplasia with myelofibrosis and malignant myelosclerosis. The pathogenesis of fibrosis in these cases may be related to disordered megakaryopoiesis and the platelet-derived cytokines that may be released. The treatment of these fibrotic cases remains problematical and further investigation is required.

Adult↗